Hard dental tissue having suffered damage due to dental caries is conventionally restored by a procedure in which an indirect restoration such as a crown, a bridge, an inlay, or an onlay, is adhered on the damaged portion of the hard dental tissue with a specific dental composition such as a dental resin cement. Alternatively, damaged hard dental tissue may be restored by using a direct restorative material which is applied as an uncured dental composition such as a dental composite, and hardened.
A dental resin cement and a dental composite are required to have low shrinkage, sufficient adhesion and high material strength. Otherwise, not only the dental composition may be released from the hard dental tissue after some time under the severe conditions of the oral environment, but also a gap may be produced at an interface between the dental composition and the teeth, and bacteria may invade onto the exposed surfaces and impose an adverse effect on dental pulp. Given that the use of a dental primer increases the complexity of a dental procedure, a simple adhesion procedure is desired which uses a dental composition which does not require a primer treatment for such various adherents.
Moreover, since adhesion of a dental composition to hard dental tissue requires the presence of acidic groups in the composition, the dental composition desirably has a high hydrolysis stability in order to avoid degradation of the composition during storage or when applied to hard dental tissue.
Japanese Patent Publication No. 2006-512466A discloses a resin cement which does not require a primer. The polymerizable composite material comprises at least one multifunctional monomer containing an acid in a concentration range of about 10-85% by weight, a non-reactive filler in a concentration range of about 1-80% by weight, a polymerization system in a concentration range of about 1.5-25% by weight, and water in a concentration range of about 0.1-25% by weight. However, since such the composition uses a single acidic monomer, sufficient adherability cannot be attained for both of enamel and dentin.
International Publication No. WO 02/092021A1 discloses a dental resin cement composition consisting of a liquid and a powder. A powder-liquid type resin cement, is inferior in handling properties upon mixing as compared with a paste-and-paste type resin cement.
Japanese Patent Publication No. 2005-65902A discloses a dental adhesive composition comprising, as an essential adhesive component, a carboxylic acid compound having one (meth)acryloyl group and one carboxyl group which are bound to an aromatic group as a polymerizable monomer containing a particular carboxylic acid group. However, such the polymerizable monomer having an ester group quickly degrades in an acidic medium.
Dental materials based on polyfunctional amides are known from U.S. Pat. No. 6,953,832 which contain specific polymerizable amides and optionally strongly acidic polymerizable monomers such as dipentaerythritol pentamethacryloyloxy dihydrogenphosphate. Filler containing compositions are suggested. However, U.S. Pat. No. 6,953,832 does not disclose a composite.